Low density parity check (LDPC) codes are a class of forward error correcting (FEC) codes, first introduced by Gallager in “Low-Density Parity-Check Codes,” IRE Transactions on Information Theory, Volume 7, January, 1962, pages 21-28, which is incorporated herein by reference. LDPC codes are also described by Ryan and Vasic in “An Introduction to LDPC Codes,” GlobeCom 2003, San Francisco, Calif., Dec. 5, 2003, which is incorporated herein by reference.
LDPC codes, as well as other code classes such as turbo codes, are often decoded using iterative decoding processes. Iterative decoding methods are described, for example, by Worthen and Stark in “Unified Design of Iterative Receivers using Factor Graphs,” IEEE Transactions on Information Theory, (47:2), February, 2001, pages 843-849, and by Richardson and Urbanke in “An Introduction to the Analysis of Iterative Coding Systems,” Proceedings of the 1999 Institute for Mathematics and its Applications (IMA) Summer program: Codes, Systems and Graphical Models, Minneapolis, Minn., Aug. 2-6, 1999, which are incorporated herein by reference.